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From Philippe <watche...@gmail.com>
Subject Re: Network traffic patterns
Date Sun, 20 Nov 2011 22:53:36 GMT
I'm using BOP.
Le 20 nov. 2011 13:09, "Boris Yen" <yulinyen@gmail.com> a écrit :

> I am just curious about which partitioner you are using?
>
> On Thu, Nov 17, 2011 at 4:30 PM, Philippe <watcherfr@gmail.com> wrote:
>
>> Hi Todd
>> Yes all equal hardware. Nearly no CPU usage and no memory issues.
>> Repairs are running in tens of minutes so i don't understand why
>> replication would be backed up.
>>
>> Any other ideas?
>> Le 17 nov. 2011 02:33, "Todd Burruss" <bburruss@expedia.com> a écrit :
>>
>> Are all of your machines equal hardware?  Since those machines are
>>> sending data somewhere, maybe they are behind in replicating and are
>>> continuously catching up?
>>>
>>> Use a tool like tcpdump to find out where the data is going
>>>
>>> From: Philippe <watcherfr@gmail.com>
>>> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
>>> Date: Tue, 15 Nov 2011 13:22:38 -0800
>>> To: user <user@cassandra.apache.org>
>>> Subject: Re: Network traffic patterns
>>>
>>> Sorry about the previous message, I've enabled keyboard shortcuts on
>>> gmail...*sigh*...
>>>
>>> Hello,
>>> I'm trying to understand the network usage I am seeing in my cluster,
>>> can anyone shed some light?
>>> It's an RF=3, 12-node, cassandra 0.8.6 cluster. repair is performed on
>>> each node once a week, with a rolling schedule.
>>> The nodes are p13,p14,p15...p24 and are consecutive in that order on the
>>> ring. Each node is only a cassandra database. I am hitting the cluster from
>>> another server (p4).
>>>
>>> p4 is doing this with 20 threads in parallel
>>>
>>>    1. read a lot of data (some columns for hundreds to tens of
>>>    thousands of keys, split into 512-key multigets)
>>>    2. process the data
>>>    3. write back a byte array to cassandra (average size is 400 bytes)
>>>    4. go back to 1
>>>
>>> According to my munin graphs, network usage is about as follows. I am
>>> not surprised at the bias towards p13-p15 as p4 is getting & storing data
>>> mainly for keys located on one of those nodes.
>>>
>>>    - p4 : 1.5Mb/s in and out
>>>    - p13-p15 : 15Mb/s in and 80Mb/s out
>>>    - p16-p24 : 45Mb/s in and 5Mb/s out
>>>
>>> What I don't understand is why p4 is only seeing 1.5Mb/s while I see
>>> 80Mb/s on p13 & p15.
>>>
>>> The way I understand this:
>>>
>>>    - p4 makes a multiget to the cluster, electing to use any node in
>>>    the cluster (IN traffic for describe the query)
>>>    - coordinator node replays the query on all 3 replicas (so 3 servers
>>>    each get the IN traffic, mostly p13-p15)
>>>    - each server replies to coordinator
>>>    - coordinator chooses matching values and sends back data to p4
>>>
>>> So if p13-p15 are outputting 80Mb/s why am I not seeing 80Mb/s coming
>>> into p4 which is on the receiving end ?
>>>
>>> Thanks
>>>
>>> 2011/11/15 Philippe <watcherfr@gmail.com>
>>>
>>>> Hello,
>>>> I'm trying to understand the network usage I am seeing in my cluster,
>>>> can anyone shed some light?
>>>> It's an RF=3, 12-node, cassandra 0.8.6 cluster. The nodes are
>>>> p13,p14,p15...p24 and are consecutive in that order on the ring.
>>>> Each node is only a cassandra database. I am hitting the cluster from
>>>> another server (p4).
>>>>
>>>> The pattern on p4 is the pattern is to
>>>>
>>>>    1. read a lot of data (some columns for hundreds to tens of
>>>>    thousands of keys, split into 512-key multigets)
>>>>    2. process the data
>>>>    3. write back a byte array to cassandra (average size is 400 bytes)
>>>>
>>>>
>>>> p4 reads as
>>>>
>>>
>>>
>

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